Heat-sensitive protein compositions (HSPC) are widely applicable in food and nutraceutical industries. For example, egg white is qualified as a multi-purpose ingredient due to its high nutritional qualities and excellent foaming and gelling properties. Many HSPCs are commercialized under liquid solution forms but dried particulate forms can be preferable as they offer longer shelf lives and enhanced ease of transport, storage, and use. In drying HSPCs, energy efficiency and product quality are the primary concerns yet achieving one concern often frustrates the purpose of the other. High-temperature drying processes can achieve the highest drying efficiencies, but can have a detrimental effect on the functional properties of heat-sensitive proteins. For example, liquid egg whites comprise about 80% to 95% water, and the energy imparted to evaporate the water can induce protein denaturation which reduces functional properties of the egg white such as foaming and gelling properties. Similarly, high temperature drying of milk can degrade bio-activity of constituent enzymes and overall product taste.
Many HSPCs are traditionally dried by spray drying methods, which include spraying an HSPC feed via rotary atomizers or nozzles into a hot drying medium to remove moisture and provide a dried particulate form. In order to operate efficiently, spray drying must be conducted at HSPC-damaging temperatures, for example temperatures above a denaturation temperature of one or more proteins. Most spray dryers operate at temperature below denaturation temperatures, but process efficiency suffers as a result. Further, spray dryer rotary atomizers and nozzles clog easily when conveying higher viscosity or particulate-containing feeds. Spray dryers also suffer from technical difficulties, particularly due to wear on rotary atomizers and nozzles which over time reduce feed flow rate conveying accuracy and increase maintenance costs and unit down-time.